Report on Loihi (United States) — September 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 9 (September 1986)
Managing Editor: Lindsay McClelland.
Loihi (United States) Earthquake swarm
Please cite this report as:
Global Volcanism Program, 1986. Report on Loihi (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 11:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198609-332000.
18.92°N, 155.27°W; summit elev. -975 m
All times are local (unless otherwise noted)
On 20 September, an earthquake swarm occurred in the vicinity of Loihi. Seven events of M 2.8-3.9 were recorded between 1900 and 2300 before seismicity declined (figure 2).
|Figure 2. Hypocenters of earthquakes in the vicinity of Hawaii and Loihi seamount, September 1986. Courtesy of USGS.|
Geologic Background. Loihi seamount, the youngest volcano of the Hawaiian chain, lies about 35 km off the SE coast of the island of Hawaii. Loihi (which is the Hawaiian word for "long") has an elongated morphology dominated by two curving rift zones extending north and south of the summit. The summit region contains a caldera about 3 x 4 km wide and is dotted with numerous lava cones, the highest of which is about 975 m below the sea surface. The summit platform includes two well-defined pit craters, sediment-free glassy lava, and low-temperature hydrothermal venting. An arcuate chain of small cones on the western edge of the summit extends north and south of the pit craters and merges into the crests prominent rift zones. Deep and shallow seismicity indicate a magmatic plumbing system distinct from that of Kilauea. During 1996 a new pit crater was formed at the summit, and lava flows were erupted. Continued volcanism is expected to eventually build a new island; time estimates for the summit to reach the sea surface range from roughly 10,000 to 100,000 years.
Information Contacts: C. Heliker, USGS Hawaiian Volcano Observatory.